There's just no way this is going to happen. They cannot restrict licensing based on hardware changes and force you to buy a new copy if, say, your motherboard dies, or your hard drive crashes, or your processor goes dead. This would get them into the hairy realm of liability - as in:

"I am a customer whose Hitachi hard drive died. Now, I have to buy a new copy of Vista because of their restrictive licensing. It is not my fault my hard drive died. Therefore, I am telling Hitachi that they need to pay for my copy of Vista."

"My ATI video card burned up. Now I'm going to make ATI buy me a new copy of Vista".

Seriously. This just won't fly. I'm sure we're not hearing the whole story.